1. Field of the Invention
This invention generally relates to remote communication terminals capable of collecting data and performing load management functions.
2. Description of the Prior Art
Several types of distribution network communication systems exist for communicating over the power-line conductors of a utility's power distribution network. The purpose of the communication system is to allow a central control station to communicate with individual or groups of utility customers. Such communications may include instructions for data acquisition or load control. In order to receive and implement these instructions the utility customer location must be equiped with some type of equipment responsive to the received instructions, such as a load management terminal.
A typical load management terminal is capable of receiving communication signals, determining which of the received signals were addressed to it, and taking appropriate action in response. Appropriate action may be to interrogate a time of day meter, shed specific loads or update a local clock. The load management terminal is also capable of transmitting meter data and other information from the customer location, through the distribution network, back to the electric utility.
In order to perform all of these functions and still be capable of mass production at cost effective prices, load management terminals are typically designed around a microprocessor. The microprocessor can perform a variety of functions such as comparing the address of a received signal to stored addresses, performing an error check on the received signal, etc., while discrete circuits and output devices, under microprocessor control, perform other necessary functions such as receiving or transmitting a communication signal, disconnecting loads, etc. The microprocessor based load management terminal is dependent upon the proper operation of the microprocessor in order to function without problems.
A microprocessor requires a set of commands, or instructions, in order to perform its intended function. It is possible for a microprocessor to become lost and to begin to execute instructions out of sequence, or to execute phantom instructions, as a result of electrical noise, system transients or the like. When the microprocessor becomes lost it must be reset, or directed to a specific instruction within a program, in order to return to a proper state of operation. The present invention is for a load management terminal having improved operating reliability due primarily to a novel reset circuit capable of detecting when the microprocessor is lost and, accordingly, resetting the microprocessor.